Cloud cover causing airport delays in Northeast

Update (3:55 p.m.): According to the Federal Aviation Administration, delays in Boston were averaging 48 minutes; at Newark 1 hour and 6 minutes; at Philadelphia 2 hours and 21 minutes.

Spreading weather-related delays in the Northeast are slowing air travel, potentially upending what had been a smooth but busy air travel day.

Some departing flights from Dulles and Reagan-National airports are being delayed because of slowdowns in Boston, Newark, New York and Philadelphia caused by excessive low-level cloud cover. Dulles and Reagan-National are experiencing similar weather conditions, according to the FAA.Travelers should check with their carriers for the latest information about flight delays, which is changing frequently.

Excessive low-lying cloud cover makes it more difficult for pilots to take off and land. As a precaution, controllers generally space out airplane landing intervals. Mike Pigott, a meteorologist at Accuweather.com, said the weather conditions are expected to remain throughout the day.